画圆

void CYuanView::OnDraw(CDC* pDC){CYuanDoc* pDoc = GetDocument();ASSERT_VALID(pDoc);// TODO: add draw code for native data hereif(m_R){CRect rect(m_point.x-m_R,m_point.y-m_R,m_point.x+m_R,m_point.y+m_R);pDC->Ellipse(rect);}}void CYuanView::OnMouseMove(UINT nFlags, CPoint point) {// TODO: Add your message handler code here and/or call defaultif(m_Flag){CRect rect;m_R=sqrt((double)(m_point.x-point.x)*(m_point.x-point.x)+(double)(m_point.y-point.y)*(m_point.y-point.y));rect.SetRect(m_point.x-m_R,m_point.y-m_R,m_point.x+m_R,m_point.y+m_R);this->Invalidate();//清除所有，包括上次的}CView::OnMouseMove(nFlags, point);}void CYuanView::OnLButtonUp(UINT nFlags, CPoint point) {// TODO: Add your message handler code here and/or call defaultm_Flag=FALSE;CView::OnLButtonUp(nFlags, point);}void CYuanView::OnLButtonDown(UINT nFlags, CPoint point) {// TODO: Add your message handler code here and/or call defaultm_Flag=TRUE;m_point=point;m_R=0;CView::OnLButtonDown(nFlags, point);}